個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另(ling)外(wai)，由電(dian)池(chi)(chi)提供的(de)安(an)全信(xin)號指示(shi)電(dian)池(chi)(chi)是否(fou)呈(cheng)現在系統中和是否(fou)有熱引(yin)起的(de)告警或(huo)在其(qi)他系統失效時是否(fou)電(dian)池(chi)(chi)失效。SBS顯著特點是安(an)全、使用容(rong)易和兼容(rong)性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太(tai)熱，則充電(dian)也將終(zhong)止。

　　SMBus 為系(xi)(xi)統(tong)和(he)(he)(he)電源管(guan)理這(zhe)樣(yang)的(de)(de)任務提供了一條(tiao)控制(zhi)總線(xian)，使用 SMBus 的(de)(de)系(xi)(xi)統(tong)，設(she)(she)備(bei)(bei)之(zhi)間(jian)發送和(he)(he)(he)接收消息都是通(tong)(tong)過 SMBus，而不(bu)是使用單獨的(de)(de)控制(zhi)線(xian)，這(zhe)樣(yang)可(ke)以(yi)節省設(she)(she)備(bei)(bei)的(de)(de)管(guan)腳數。 　　使用 SMBus，設(she)(she)備(bei)(bei)還(huan)可(ke)以(yi)提供它(ta)的(de)(de)生產信息，告訴系(xi)(xi)統(tong)它(ta)的(de)(de)型號，部件(jian)號等，針對掛(gua)起事件(jian)保存它(ta)的(de)(de)狀態，報告不(bu)同(tong)類別的(de)(de)錯(cuo)誤(wu)，接收控制(zhi)參數，并(bing)返回它(ta)的(de)(de)狀態等。 　　SMBus器(qi)件(jian)存在(zai)現有(you)7層(ceng)OSI網(wang)絡模(mo)型中(zhong)的(de)(de)前3層(ceng)，即物理層(ceng)，數據鏈路層(ceng)和(he)(he)(he)網(wang)絡層(ceng)。 　　SMBus最初的(de)(de)目(mu)的(de)(de)是為智(zhi)能電池，充(chong)電電池和(he)(he)(he)與其他系(xi)(xi)統(tong)通(tong)(tong)信的(de)(de)微(wei)控制(zhi)器(qi)之(zhi)間(jian)的(de)(de)通(tong)(tong)信鏈路而定義的(de)(de)。SMBus也被用來連接各種(zhong)設(she)(she)備(bei)(bei)，包括電源相(xiang)關(guan)設(she)(she)備(bei)(bei)，系(xi)(xi)統(tong)傳感器(qi)，EEPROM通(tong)(tong)訊(xun)設(she)(she)備(bei)(bei)等等。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范(fan)的全部安全要求，包括(kuo)3分鐘定(ding)時(shi)器（保(bao)護(hu)SMBus通信換效和喚醒模式期間鋰離子(zi)電(dian)(dian)池過充電(dian)(dian)）。硬件(jian)可編程電(dian)(dian)注和電(dian)(dian)壓限制提供另外等(deng)級保(bao)護(hu)，這(zhe)種(zhong)保(bao)護(hu)由失效軟件(jian)不可能改(gai)變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控制器(qi)，兩個控制充電器(qi)參量的10位DAC，一(yi)(yi)個熱敏電阻安(an)全信號(hao)譯碼器(qi)，硬(ying)件電壓和電流(liu)限制譯碼器(qi)和一(yi)(yi)個SMBus控制器(qi)單元（見圖1）。

 智(zhi)能(neng)電(dian)(dian)(dian)池(chi)(chi)或系(xi)統控(kong)制器(qi)通過(guo)SMBus接口命(ming)令對恒(heng)漢和恒(heng)壓限值進行編程。降(jiang)壓變(bian)壓器(qi)用N-溝MOSFET做(zuo)為開關，使成本降(jiang)低(di)、高效率工作。熱敏電(dian)(dian)(dian)阻安全檢測電(dian)(dian)(dian)路檢測電(dian)(dian)(dian)池(chi)(chi)存在(zai)或確定(ding)電(dian)(dian)(dian)池(chi)(chi)溫度是否允許安全充(chong)電(dian)(dian)(dian)。

當(dang)通(tong)過(guo)SMBus傳(chuan)輸接(jie)收(shou)恒(heng)流(liu)(liu)值時，它被RILIMIT定標和限制到(dao)低于編(bian)程值。此修正值編(bian)程電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)DAC，設置DC充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)DAC是(shi)10位△∑DAC，當(dang)希望充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)時，它從PROG引腳(jiao)吸(xi)收(shou)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)（見圖(tu)2）。放大器(qi)PROG引腳(jiao)吸(xi)收(shou)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)（見圖(tu)2）。放大器(qi)CAI感測RSENSE上的壓降并使(shi)(shi)此電(dian)(dian)(dian)(dian)(dian)壓跨接(jie)到(dao)RS2（200Ω）；流(liu)(liu)經RS2的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通(tong)過(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)鏡像做為PROG引腳(jiao)上的上接(jie)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。流(liu)(liu)經RS2電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)與來自PROG引腳(jiao)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相(xiang)匹配(pei)由(you)CA2實現恒(heng)流(liu)(liu)工作。由(you)于DAC輸出是(shi)一串脈沖，所以需要平滑電(dian)(dian)(dian)(dian)(dian)容器(qi)對脈沖濾波(bo)使(shi)(shi)其變為DC。

  LTC1759需(xu)(xu)要(yao)(yao)兩個(ge)電(dian)源(yuan)。PWM電(dian)路(lu)在(zai)(zai)(zai)墻式適配器(qi)電(dian)源(yuan)斷(duan)開時(shi)(shi)(shi)(shi)直接通過Vcc引(yin)腳運行(xing)，邏(luo)輯功(gong)能運行(xing)與VDD電(dian)源(yuan)無關。PWM電(dian)路(lu)在(zai)(zai)(zai)去掉AC電(dian)源(yuan)時(shi)(shi)(shi)(shi)能進(jin)入40μA微功(gong)率(lv)停機(ji)模式，使邏(luo)輯和SMBus工作(zuo)能保持運行(xing)，這是Intel ACPI標準所需(xu)(xu)要(yao)(yao)的(de)。這種分(fen)離電(dian)源(yuan)也使邏(luo)輯和SMBus能根據系統(tong)設計為員的(de)需(xu)(xu)要(yao)(yao)運行(xing)在(zai)(zai)(zai)3V和5V.為使LTC1759邏(luo)輯功(gong)耗最小，邏(luo)輯電(dian)流(liu)由時(shi)(shi)(shi)(shi)鐘電(dian)路(lu)激勵，時(shi)(shi)(shi)(shi)鐘電(dian)路(lu)當無動作(zuo)時(shi)(shi)(shi)(shi)停機(ji)并蘇(su)醒服務于SMBus動作(zuo)或產生中斷(duan)。一(yi)旦(dan)請求服務，LTC1759便返回到(dao)休(xiu)眠。

　　當去掉(diao)AC電(dian)(dian)源(yuan)或去掉(diao)電(dian)(dian)池(chi)時，通過(guo)CHGEN-SDB引腳(jiao)組合發(fa)生PWM停機。LTC1759通過(guo)DCDIV通腳(jiao)檢測AC損耗。閾值通常設置恰(qia)好低于墻式(shi)適配的(de)最小有效電(dian)(dian)壓(ya)。AC電(dian)(dian)源(yuan)狀態通過(guo)SMBus可(ke)由系統(tong)讀出。UV引腳(jiao)只用于置PWM電(dian)(dian)路(lu)進入(ru)微功率停機狀態，它(ta)直(zhi)接連到墻式(shi)適配器電(dian)(dian)源(yuan)。

　　在(zai)設計(ji)中(zhong)電感器(qi)選擇不是關鍵，這是因為充電器(qi)的環路(lu)響(xiang)應(ying)在(zai)意地設置很慢。實際(ji)的低(di)限值為15μH左右，低(di)值電感器(qi)將產生較(jiao)高(gao)的紋波電流，在(zai)輸(shu)出需要較(jiao)低(di)ESR電容器(qi)。

　　輸出電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的選擇對ESR（等效串聯電(dian)(dian)(dian)(dian)阻(zu)）不是很苛(ke)刻，但(dan)必須處理來自充(chong)電(dian)(dian)(dian)(dian)器的所有(you)紋(wen)波電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。不用(yong)(yong)考慮(lv)電(dian)(dian)(dian)(dian)池(chi)的紋(wen)波電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，因為(wei)充(chong)電(dian)(dian)(dian)(dian)器有(you)效阻(zu)抗(kang)遠遠大于(yu)(yu)電(dian)(dian)(dian)(dian)感器的ESR。很多電(dian)(dian)(dian)(dian)池(chi)組具有(you)內部(bu)串聯保護MOSFET，這提高(gao)了(le)電(dian)(dian)(dian)(dian)池(chi)ESR。在(zai)多電(dian)(dian)(dian)(dian)池(chi)配置(zhi)中也有(you)與(yu)電(dian)(dian)(dian)(dian)池(chi)串聯的功率路由(you)MOSFET，進(jin)一(yi)步增(zeng)加了(le)電(dian)(dian)(dian)(dian)池(chi)ESR。從(cong)充(chong)電(dian)(dian)(dian)(dian)器觀點，輸入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器ESR可(ke)高(gao)達(da)1Ω，使電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器選擇范圍寬。當(dang)采用(yong)(yong)電(dian)(dian)(dian)(dian)阻(zu)或(huo)電(dian)(dian)(dian)(dian)子負載時(shi)，可(ke)能(neng)(neng)會(hui)發生某(mou)種不穩定性。增(zeng)加300Ω電(dian)(dian)(dian)(dian)阻(zu)器與(yu)PROG引腳電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器串聯或(huo)在(zai)輸出置(zhi)10μF電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器能(neng)(neng)改善穩定性。在(zai)輸出不需要用(yong)(yong)陶瓷(ci)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器，因為(wei)在(zai)很輕負載電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)聲(sheng)頻(pin)下開關變換(huan)器變得不連(lian)接和在(zai)下降周期開始時(shi)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器會(hui)造成噪聲(sheng)，應該采用(yong)(yong)鉭電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)。輸入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)選擇由(you)充(chong)電(dian)(dian)(dian)(dian)器輸入(ru)(ru)(ru)紋(wen)波電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)（一(yi)般為(wei)最大輸出電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)的1/2）決定。對于(yu)(yu)4A充(chong)電(dian)(dian)(dian)(dian)器建(jian)議用(yong)(yong)22μF（50V）陶瓷(ci)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器，它(ta)一(yi)般可(ke)處理2A紋(wen)波電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。

　　從電(dian)(dian)池(chi)(chi)到(dao)墻式適配(pei)器(qi)的電(dian)(dian)流保(bao)護由P-溝MOSFET（Q1）提供。電(dian)(dian)壓(ya)(ya)比較器(qi)監控跨接在MOSFET上(shang)的電(dian)(dian)壓(ya)(ya)而(er)且當墻式適配(pei)降到(dao)電(dian)(dian)池(chi)(chi)電(dian)(dian)壓(ya)(ya)之上(shang)小于200mV時關閉MOSFET。盡管(guan)價廉的二極管(guan)可用于替代以MOSFET，但(dan)MOSFET只增加(jia)100mV到(dao)0.4V低壓(ya)(ya)差工(gong)作模式而(er)不(bu)產生額外的熱量。在沒有(you)電(dian)(dian)池(chi)(chi)起動時間，采用MOSFET附(fu)加(jia)二極管(guan)使墻式適配(pei)器(qi)電(dian)(dian)源能達(da)到(dao)Vcc引腳并為(wei)PWM控制電(dian)(dian)路供電(dian)(dian)。

　　主要(yao)(yao)的(de)補償是(shi)d PROG引腳(jiao)上進行；然而DAC脈沖濾波要(yao)(yao)求確定電(dian)容器(qi)有(you)效值。脈沖紋波電(dian)流必(bi)(bi)須小平200mV或(huo)環路起伏（在輕載充電(dian)電(dian)流時出現的(de)環路不(bu)穩(wen)定性）。Vc引腳(jiao)電(dian)容器(qi)的(de)主要(yao)(yao)功能(neng)是(shi)提(ti)供自(zi)啟動支持(chi)。必(bi)(bi)須有(you)一(yi)個1.5K電(dian)阻器(qi)與Vc引腳(jiao)電(dian)容器(qi)串聯以能(neng)恰當停機。

　　從熱觀點考慮，輸出電(dian)(dian)壓(ya)在電(dian)(dian)池(chi)(chi)溫(wen)度充(chong)電(dian)(dian)范(fan)圍內保持大約0.5%精(jing)度。精(jing)度越(yue)高，電(dian)(dian)流充(chong)電(dian)(dian)容量就越(yue)大，而更重要是在電(dian)(dian)池(chi)(chi)中與電(dian)(dian)壓(ya)基充(chong)電(dian)(dian)終端電(dian)(dian)路有關的問題就會(hui)更少。

　　關于SMBus加速泵，AC適配電(dian)流限制，安全信號感測，安全電(dian)壓和電(dian)流范圍設計等問題在此就不一一詳述。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。